#include<iostream>
#include<fstream>
using namespace std;

enum status {up,down};
 
struct DataItem{
	char node_id[50];
    long double time;
	status state; 
};

class DataSource{
public:
	DataSource();
	~DataSource();
	struct DataItem* NextItem();
private:
	ifstream finput;
	//char* file_name;
	char* current_node;
    char updown;
	unsigned int session_number;
	unsigned int index;
	long double time;
	DataItem    data_item;
};
